Oxygen in my Co2 tank?

I get my Co2 tank filled at a can redemption place. My “local” homebrew shop is an hour away and just does tank exchange. However when I got my tank filled today I didn’t think about it right away the guy only charged me for 4LBS and said there’s prolly a pound of oxygen in it because he had to switch tanks in between filling. Is this legit? The guy asides from knowing how to fill it doesn’t seem to be the most creditable character. To me it doesn’t make any sense that the large tanks would contain a cap of oxygen or anything like that but I have no actual knowledge of them. Just checking before I hook it up.

That sounds like BS. To get oxygen in there, you’d actually have to pump it in under pressure. How would this happen when switching tanks? Your beer certainly won’t benefit if it’s true.

I know it’ll F my beer up quick and to me its complete BS but I don’t want to find out if it isn’t. I have a delicious brown and wheat pale ale that I need to carb and would be pissed if its true.

You should have opened the valve and drained the tank and told him to refill it with CO2, just to make a point. But I think he’s wrong.

Ya I just wasn’t even thinking about it right off the top of my head.

Yeah this is not possible. He would of had to switch from a CO2 tank to a Oxygen tank in order to do that. When the tank that he was filling from became to low to fill yours anymore no oxygen can enter it will just equalize. Then inorder to switch tanks he would have to close the valve on your tank, close the valve on the tank that could no longer fill anymore (it would still have co2 in it just not enough to fill your tank), then hook a new tank up.

Its just like putting CO2 into your keg you have to purge the oxygen out with CO2 Thats what happens when he starts to fill your tank.

“A pound of oxygen” taking up space in a CO2 tank, now that’s funny. :cheers:

No worries, as it seems the guy doesn’t know what he is talking about. Switching source tanks is not an issue and you’d really have to work to get another gas mixed in, not just disconnect and connect CO2 tanks.